It is known art that gas burners for domestic ovens, or grills can comprise a first extended chamber for distributing the gas-primary air fuel mixture, immediately placed downstream to the mixing tube having a Venturi effect, and a second delivery chamber, fluidly connected to the first one, provided with outflow holes outwardly for such a fuel mixture (flame holes). The shape and dimensions of the fuel mixture passageways from the distribution chamber to the delivery chamber, as well the shape of the delivery chamber and of the corresponding outflow holes, determines the local thermodynamic conditions of the mixture inside the burner, particularly its point by point pressure and concentration, and thereby determines the flame shape, profile, and distribution outside the outflow holes of the second chamber.
For example, the U.S. Pat. No. 3,156,292, in the name of ROSS, describes a similar gas burner for ovens, in which a tubular distribution chamber, longitudinally extending in the inflow direction of the fuel mixture, and situated downstream from the mixing tube, is fitted in an outer case provided with flame holes. The outer case defines, between its upper wall and the distribution tubular chamber itself, a delivery chamber, that is fluidly connected to the distribution chamber via some passageways, longitudinally extending, and obtained over the walls of the latter. Such longitudinally extended passageways have the object to guarantee the homogeneous gas inflow from the distribution chamber to the mixing chamber and thereby guarantee some homogeneity in the flame distribution and profile.
Such a solution, although aiding a fair burner operation, does not consider the pressure difference generating within the tubular distribution chamber because of the sudden stop of the mixture flow at the closed end, opposite to the mixing tube, of the distribution chamber itself, which is opposite to the mixing tube.
Particularly, the mixture flow within the tubular distribution chamber, given by the gas outflow from the corresponding injector, longitudinally proceeds from the Venturi tube towards the closed end of the distribution chamber itself, where it encounters the ending closed wall of the latter, that will obstruct, divert and render the flow itself incoherent. Because of this, within the distribution chamber a non-null pressure gradient is generated, whereby the pressure is locally greater at the closed end of the distribution chamber and is locally smaller at the outlet section of the mixing tube.
Such a pressure gradient, as it will be evident to a person skilled in the art, will cause a non-homogeneous distribution of the mixture in the burner and then, even if in the presence of an outer delivery chamber, separated from the tubular distribution chamber, will generate an heterogeneous distribution of the flames, and consequently a non-constant geometrical distribution of the temperature and heat from the burner.
One attempt to solve this problem in International Patent Application WO 2004/005799, in the name of CAST srl, describes an extended burner for ovens of the type comprising a tubular extended distribution chamber of the fuel mixture situated downstream the gas and primary air mixing tube with a Venturi effect (Venturi tube). The mixture distribution chamber, for some length starting from the Venturi tube, is situated in fluid communication, by some sort of a longitudinal coil, with an outer delivery chamber provided with flame holes.
The described structure of such a coil is provided by two longitudinal ribs inside the burner, reciprocally and transversally spaced, and of height lower than the burner chamber height, and provides some walls disposed to carry part of the mixture flow to the delivery chamber, which is situated sideways to the tubular distribution chamber, thereby forming some sort of a trap for the mixture, which would reach a higher pressure at the flame holes being present in the delivery chamber.
Such a higher pressure, that would occur only at those flame holes of the burner placed in the delivery chamber in a position near the Venturi tube, would be sufficient to compensate the greater pressure occurring at the burner end opposite from the Venturi tube, wherein the flame holes are directly obtained into the distribution chamber and there is not any outer delivery chamber, thereby concurring in regulating the distribution of the burner flames. This solution described in the CAST application tried to solve the problem of the existence of a pressure gradient in the mixture within the distribution chamber of the burner, but, apart from resulting practically difficult to put into action, it does not achieve, within the main distribution chamber or within the delivery chamber, a sufficient homogeneity in distributing the local pressure of the mixture thereby making the flames regular and homogeneous along the whole burner.
It is an object of the present invention to realize a burner for domestic ovens or grills that does not have the drawbacks of the oven burners known in the art exhibiting a regular flame distribution for the whole longitudinal extension of the burner itself.
It is therefore an object of the present invention to provide a burner for ovens of the type comprising a Venturi tube for mixing fuel gas and primary air and a longitudinally extended distribution chamber, located downstream the Venturi tube, exhibiting on its own inside a regular distribution of the mixture pressure for the whole burner extension, at least at the corresponding flame holes.
It is another object of the present invention to provide an oven or grill burner of the aforementioned type, that allows to have regularly and homogeneously distributed flames for the whole development of the burner itself.